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  • 1
    Electronic Resource
    Electronic Resource
    (η-Cyclopentadienyl)[1-4-η-(5exo-cyclopentadienyl-1,3-cyclopentadien)]cobalt(I) (1983)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 66 (1983), S. 185-191 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of cobaltocene with cyclopentadiene and air results in the formation of the title compound; its structure has been elucidated by spectroscopic and X-ray methods.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19830660120
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  • 2
    Electronic Resource
    Electronic Resource
    Cascade Cyclizations of Terpenoid Polyalkenes Triggered by Photoelectron Transfer - Biomimetics with PhotonsPresented in part at the ‘10th International Conference on Organic Synthesis (IUPAC-ICOS 10)’, 11-16 December, 1994, Bangalore, India, and at the ‘IUPAC-POST ICOS 10 Symposium’, 19-20 December, 1994, Trivandrum, India. For earlier work in this series, see [1].This paper is dedicated to Prof. Hans-Dieter Scharf, RWTH Aachen, on the occasion of his 65th birthday. (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 2065-2076 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Light-induced cyclizations of suitably functionalized polyalkene terpenoids, such as geranyl, all-trans-farnesyl, and all-trans-geranylgeranyl derivatives, via formation of radical cations are proven to be a powerful method for the single-step synthesis of mono- and mostly all-trans-fused polycyclic compounds from readily available precursors. Whereas some of these highly stereo- and chemoselective transformations required the use of micel ar media, they can now be conveniently performed in homogeneous solutions upon suitable choice of the electron acceptors and of the functionality pattern of the polyalkene substrates. Moreover, the mode of cyclization, i.e., 6- vs. 5-membered ring formation and termination of the cyclization cascades, are steered efficiently by the substituents of the polyalkenes (polyalkenyl acetate vs. α,β-unsaturated ethyl polyalkenoate and polyalkene-1,1-dicarbonitrile). At the same time, the protic solvents used add highly stereoselectively to the ω-alkene sites of the polyalkens in anti-Markovnikov sense which strongly suggests that radical cations are intercepted. Interestingly, the transformations achieved here upon photoelectron transfer parallel the biosynthetic paths of non-oxidative terpene cyclizations which are thought to occur purely by protonation of the isoprenoid polyalkenes.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780815
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  • 3
    Electronic Resource
    Electronic Resource
    Reactivity of the Heavier Group-13 Monochlorides [{CH(SiMe3)2}2AlCl], InCl, TlCl, and of the Elements Ga and Hg Towards the Unsupported Ni-Ni Bond of [{(η5-Cp)Ni(PEt3)}2]  -  A Straightforward Synthetic Approach to the Synthesis of Mixed Main-Group/Transition-Metal Clusters Containing Unsupported Metal-Metal BondsDedicated to Prof. Dr. G Hutter on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1433-1440 
    Details
    ISSN: 0009-2940
    Keywords: Metal - metal bonds ; Insertion reactions ; Group-13 monochlorides ; Main-group elements ; Nickel ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dinuclear compound [{(η5 - Cp)Ni(PEt3)}2] (1) containing an unbridged Ni-Ni bond reacts with the heavier group 13 monochlorides [{CH(SiMe3)2)2}AlIIICl], InCl, and TlCl by scission of the metal-metal bond. In the case of InCl and TlCl the chloro-bridged dimmers [{(η5-Cp)Ni(PEt3)2ECl2Ecl}2] (E = In 2, Tl 5) were formed. The Tl compound 5 is unstable and decomposes via disproportionation a and formation of the halogen-free Tl [III] compound [{(η5-Cp)Ni(PEt3)}3Tl] (6). 2 can be dehalogenated with activated magnesium to yield the halogen-free In [III] compund [{(η5-Cp}Ni(PEt3)}3In] (4). The Ga analogue of 4 and 6 [{(η5-Cp)Ni(PEt3)}3Ga] (7) is accessible by a conproportionation of 1 with Ga metal in refluxing THF. In contrast to InCl and TlCl the aluminium (III) monochloride [{CH(SiMe3)2}2AlCl] reacts with 1 by a ligand redistribution reaction and formation of the salt [{(η5-Cp)Ni(PEt3)2]+-[{CH(SiMe3)2]2AlCl]2-. (8). Elemental Hg or Mg amalgam show the same activity as elemental Ga towards 1 and insert into the Ni—Ni bond by forming the linear Hg-bridged complex [(n3-Cp)Ni(PEt3)]2Hg] (9). The molecular structures of 2, 4, 8, and 9 were determined by X-ray crystallography. The In atom in 4 has a distorted trigonal-planar configuration with the central In atom being surrounded by three [(n5-Cp)Ni(PEt3)] fragments. 4 represents the first Ni-In cluster containing exclusively unsupported In - Ni bonds, as well as the first carbonyl-free Ni - In cluster. On the basis of spectroscopic data the same structure is assigned to the Ga and Tl analogues of 4. The Ni—Hg—Ni arrangement in 9 is exactly linear, as determined by X-ray crystallography.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301013
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis, Structure, Electrochemistry and Reactivity of the Bis(μ-σ-stannanediyl)dinickel Butterfly Cluster [{{(SiMe3)2CH}2Sn-Ni(η5-Cp)}2](Ni2-Sn2) (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1987-1993 
    Details
    ISSN: 1434-1948
    Keywords: Cluster ; Nickel ; Tin ; Bimetallic complexes ; Electrochemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Addition of stannylene [{(SiMe3)2CH}2Sn:] (2) to the unbridged homobimetallic Ni-Ni bond of [{PEt3Ni(η5-Cp)}2] (1) gives the heterobimetallic, tetranuclear compound [{{(SiMe3)2CH}2Sn-Ni(η5-Cp)}2] (3) with a butterfly arrangement and leaves the Ni-Ni bond of 1 intact. Elimination of both PEt3 ligands from the starting material 1 is observed, probably due to steric restraints. Compound 3 is formally related to the hypothetical closo-borane B4H42-. The Ni-Ni bond in 3 is only slightly elongated [2.454(3) Å] when compared to the starting material 1 [2.41(1) Å]. Compound 3 displays a butterfly arrangement with a hinge angle of 62.5°. An alternative route to 3 is by a direct reaction between nickelocene (5) and Lappert's stannylene [{(SiMe3)2CH}2Sn:] in 63% yield. Treating 3 with water results in the cleavage of an Ni-Sn bond and subsequent opening of the cluster cage of 3 to form the trinuclear compound [(η5-Cp)Ni{Sn(CH(SiMe3)2}2OH] (6) having an Sn-OH-Sn bridge. The hydroxy proton in 6 can be exchanged by deuterium within a few minutes, as determined by 1H-NMR spectroscopy, giving the monodeuterio product, [D1]-6. Compound 6 is reactive towards acetonitrile, leading to cleavage of one Ni-Sn bond, elimination of one [{(SiMe3)2CH}2Sn:] unit, and formation of the organotin hydroxo complex [{(SiMe3)2CH}2(OH)Sn-Ni(η5-Cp)(CH3CN)] (7). In this complex, acetonitrile is coordinated to Ni via its σ lone pair, bearing the OH ligand in a terminal bonding mode to tin.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    η6-(1-oxobenzocyclobutene)tricarbonylchromium(0): Preparation, reduction, and ring-opening/cycloaddition chemistry of the 1-hydroxybenzocyclobutene complexDedicated to Professor Günther Wilke on the occasion of his 70th birthday. (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 253-265 
    Details
    ISSN: 0947-3440
    Keywords: Bicyclo[4.2.0]octa-1,3,5-triene ; Chromium complexes ; [4+2] Cycloadditions ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The syntheses of the tricarbonylchromium complexes 2 and 3 of 1-oxobenzocyclobutene and 1-hydroxybenzocyclobutene are described. Alcoholate 6 of 3 undergoes a ring opening to the corresponding ortho-quinodimethane intermediate between -30 and -20°C, which is trapped by dienophiles with high diastereoselectivity. While with most dienophiles products with a 1,2-cis configuration (7, 8, 10) are formed, vinyl sulfones react in an exo-selective cycloaddition with formation of 1,2-trans-configurated cycloadducts (12, 13). The configuration of the cycloadduct with phenyl vinyl sulfone is confirmed by an X-ray crystal structure analysis. As one of the important aspects of the chemistry of benzocyclobutene complexes is the chirality of compounds like 2 and 3, the enantiomeric resolution has been achieved via the semioxamazones of ketone 2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199519950235
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  • 6
    Electronic Resource
    Electronic Resource
    1,2,4,6-Tetraorganophosphorinylnickel-KomplexeHerrn Professor Dr. Karl Dimroth zum 70. Geburtstag gewidmet. (1981)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1981 (1981), S. 1147-1161 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,2,4,6-Tetraorganophosphorinylnickel ComplexesThe reaction of nickel(II) acetylacetonate with 2,4,6-triphenylphosphabenzene (1) and ethoxy(diethyl)aluminium results in the formation of [bis(1-ethyl-2,4,6-triphenylphosphorinyl)nickel]-(ethylene)-P,P′-nickel (2). The ethylene molecule in 2 can be displaced by 3,3-dimethylcyclo-propene (3), the alkynes 4 and 5, tricyclohexylphosphane (6) or 1 to give the corresponding nickel complexes 7-11. The two phosphorinyl ligands in these complexes bridge a Ni-Ni unit in a sandwich form.  -  1H- and 31P-NMR measurements indicate that the η3-allyl and ene functions in 7-11 as well as in bis(1-ethyl-2,4,6-triphenylphosphorinyl)iron (13) undergo valence isomerization. The ene moiety in 13 is complexed to the iron.
    Notes: [Bis(1-ethyl-2,4,6-triphenylphosphorinyl)nickel](ethylen)-P,P′-nickel (2) wird durch Reaktion von Nickel(II)-acetylacetonat mit 2,4,6-Triphenylphosphabenzol (1) und Ethoxy(diethyl)aluminium erhalten. Bei 2 läβt sich Ethylen durch 3,3-Dimethylcyclopropen (3), die Alkine 4 und 5, Tri-cyclohexylphosphan (6) oder 1 zu den entsprechenden Nickelkomplexen 7-11 verdrängen. In diesen Komplexen überbrücken beide Phosphorinylliganden sandwichartig eine Ni  -  Ni-Einheit.  -  Nach 1H- und 31P-NMR-Messungen erfolgt in den Phosphorinyl-Liganden ber 2, 7, 8 und 11 sowie bei Bis(1-ethyl-2,4,6-triphenylphosphorinyl)eisen (13) Valenzisomerisierung zwischen η3-Allyl- und En-Funktion. Bei 13 ist der En-Teil an Fe komplex gebunden.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198119810619
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  • 7
    Electronic Resource
    Electronic Resource
    1,2,3-Triazine, III Synthese von N-Aminopyrazolen und deren Oxidation zu 1,2,3-Triazinen. Molekülstruktur des 1,2,3-Triazins (1985)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1985 (1985), S. 1732-1751 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,2,3-Triazines, III. - Synthesis of N-Aminopyrazoles and their Oxidation to 1,2,3-Triazines. Molecular Structure of 1,2,3-TriazineOxidation of the N-aminopyrazoles 4a - i affords the 1,2,3-triazines 5a - i. Spectra and reactions - such as oxidation, reduction, and cycloaddition reactions - of some 1,2,3-triazines 5 are described. The X-ray analysis of 5a is presented.
    Notes: Die Oxidation der N-Aminopyrazole 4a - i liefert die 1,2,3-Triazine 5a - i. Es werden Spektren und Reaktionen - wie Oxidation, Reduktion und Cycloadditionen - einiger 1,2,3-Triazine 5 beschrieben. Die Röntgenstrukturanalyse für 5a wird angegeben.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198519850903
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  • 8
    Electronic Resource
    Electronic Resource
    Structure of Two Oxidation Products of β-Lumicolchicine: A Remarkable Reaction with Active Manganese Dioxide (1989)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1989 (1989), S. 1075-1079 
    Details
    ISSN: 0170-2041
    Keywords: β-Lumicolchicine, oxidation with active manganese dioxide, oxidation with m-chloroperbenzoic acid ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Struktur zweier Oxidationsprodukte des β-Lumicolchicins: Eine ungewöhnliche Reaktion mit aktivem MangandioxidZwei ungewöhnliche Reaktionsweisen von MnO2 und m-Chlor-perbenzoesäure mit der tetrasubstituierten C=C-Bindung von β-Lumicolchicin (1-β) werden beschrieben. Aktiver Braunstein oxidiert die 7a,10b-Cyclobutendoppelbindung, wobei in 10b-Position eine Hydroxygruppe eingeführt und am C-Atom 7a unter Einbeziehung der Acetamido-Seitenkette ein 2-Oxazolinring geschlossen wird (2). Mit m-Chlorperbenzoesäure ergibt 1-β kein Epoxid, sondern unter Öffnung des Vierrings ein 1:1-Addukt (3). Die Kristallstrukturanalyse von 2 läßt intermolekulare Wechsel-wirkungen zwischen den OH-Gruppen und den Stickstoffatomen erkennen. 13C-NMR-Spektroskopie mit Doppelquantenkohärenz (INADEQUATE-Pulsfolge) zeigt, daß 2 in Lösung die gleiche Struktur wie im Kristall besitzt und beweist die Struktur von 3. Außer den 13C-NMR-Signalen von 2 und 3 werden auch die der stereoisomeren Lumicolchicine 1-β und 1-γ zugeordnet. Ferner werden die 13C, 13C-Kopplungskonstanten für 2 und 3 ermittelt.
    Notes: Two unusual reaction types of MnO2 and of m-chloroperbenzoic acid with the tetrasubstituted C=C bond of β-lumicolchicine (1-β) are presented. Active MnO2 oxidizes the 7a,10b cyclobutene double bond by adding a hydroxy group to the position 10b while the acetamido side chain is used to close a 2-oxazoline ring in position 7a (2). m-Chloroperoxybenzoic acid splits the cyclobutene ring of 1-β and forms a ketonic 1:1 adduct (3) instead of an epoxide. X-ray structure analysis of 2 reveals intermolecular interaction between the hydroxy groups and the nitrogen atoms. 2D-INADEQUATE 13C-NMR spectroscopy establishes structure 2 in solution, proves the structure of 3, and allows also to assign the 13C-NMR signals of the tetracyclic skeleton of the stereoisomeric lumicolchicines 1-β and 1-γ. Furthermore, 13C,13C coupling constants were determined for 2 and 3.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198919890271
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  • 9
    Electronic Resource
    Electronic Resource
    Enhydrazine, 38. Unterscheidung von 1,5,6,7-Tetrahydro-4H- und 2,5,6,7-Tetra-hydro-4H-indazol-4-onen im 13C-NMR-Spektrum (1985)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1985 (1985), S. 794-801 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Enhydrazines, 38. Discrimination between 1,5,6,7-Tetrahydro-4H- and 2,5,6,7-Tetrahydro-4H-indazol-4-ones in the 13C NMR SpectrumFrom the title compounds the isomeric pairs 1a, b, 4a, b, and 5a, b were prepared. The spectroscopic properties of the regioisomers were investigated. Only the 13C NMR signals of the C atoms 3 and 7 a are significantly different within a pair and can be used for a reliable assignment. The structure of 1b was assigned by an X-ray analysis.
    Notes: Von den Titelverbindungen wurden die Isomerenpaare 1a, b, 4a, b und 5a, b dargestellt. Von den spektroskopischen Eigenschaften der Regioisomeren sind nur die 13C-NMR-Signale der C-Atome 3 und 7 a innerhalb eines Paares signifikant verschieden und für eine sichere Zuordnung geeignet. 1b wurde durch eine Röntgenstrukturanalyse gesichert.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198519850415
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  • 10
    Electronic Resource
    Electronic Resource
    Allylmetall-Verbindungen, 1 (-)- und (+)-π-Pinenylnickelhalogenide sowie (-)- und (+)-Bis(π-pinenyl)nickel - Molekül- und Kristallstruktur von (+)-Bis(π-pinenyl)nickel (1974)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1974 (1974), S. 1820-1830 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Allyl Metal-Compounds, I. - (-)- and (+)-π-Pinenylnickel Halides and (-)- and (+)-Bis(π- pinenyl)nickel - Molecular and Crystal Structure of (+)-Bis(π-pinenyl)nickelThe title compounds have been prepared by three and five stage syntheses starting from (-)-(1S,5S)-β-pinene and (+)-(1R,5R)-α-pinene, respectively. The halides may be used to separate racemic mixtures of chiral phosphines. The structure of (+)-bis(π-pinenyl)nickel has been determined by a three dimensional X-ray analysis.
    Notes: Ausgehend von (-)-(1S,5S)-β-Pinen und von (+)-(1R,5R)-α-Pinen gewinnt man in 3- bzw. 5 stufigen Synthesen die im Titel genannten Nickelkomplexe. Die Halogenide eignen sich zur Racemattrennung chiraler Phosphine. Die Struktur des (+)-Bis(π-pinenyl)nickels ergibt sich aus einer dreidimensionalen Röntgenstrukturanalyse.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.197419741112
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